1. Field of the Invention
The present invention relates to a fastener, in particular to a screw with removable element.
2. Description of the Related Art
A conventional screw 1 for screwing into metal objects is shown in FIG. 1 and generally includes a head 11, a shank 12 connecting thereto, a plurality of threads 13 defined around the shank 12, and a tip section 14 formed at the end of the shank 12. When the screw 1 is applied for screwing roofing objects, users used to climb on the roof and use a tool to rotate the head 11. The screw 1 is thus driven into the metal objects (not shown) by the tip section 14 and threads 13 to bore therethrough. However, the screw 1 may be facilely screwed in but hardly taken out of the surface of objects, namely users often need to climb on the roof and repeat the above operation for repairing the objects or loosening and tightening the screw, which makes burden and damages in operation.
Shown in FIG. 2, a screw 2 made for improving the above shortcomings includes a shank 21 and a tip section 22. The shank 21 fabricated of a stainless steel comprises a plurality of threads 211 spirally arranged thereon, a head 212 disposed at one end thereof, and a polygonal recess 213 at the other end. A tip section 22 made of another kind of harden metal respectively forms a drilling portion 221 and an insertion 222 at both ends thereof. Particularly, the tip section 22 can be removed from the shank 21 and repeatedly used after securing the objects to the roof, and users simply put a tool (not shown) into the recess 213 to reversely tighten or loosen the screw 2 without climbing on the roof very often.
As seen in FIG. 3, in practical, the insertion 222 is initially put into the recess 213, and then the tip section 22 forms a track 31 through the metal objects 3 while rotating the head 212; nevertheless, the shank 21 may not entirely follow the track 31 under the impediment of the diameter of threads 221, and which results in hesitating the movement of the screws 2 at the connection of the shank 21 and the tip section 22 and making the screw 2 unable to be substantially drilled into the objects 3. Threads 211 are facilely broken under the forced drilling although successfully screwing the screw 2 therein.